Insecure functionality - File Creation
Need
Enforce server-side validation and authorization for file creation operations
Context
- Usage of Ruby 2.0+ for developing Ruby applications
- Usage of Rails framework for building web applications
Description
Non compliant code
class FileController < ApplicationController
before_action :authenticate_user!
def create
@file = File.new(file_params)
if @file.save
render json: @file, status: :created, location: @file
else
render json: @file.errors, status: :unprocessable_entity
end
end
private
def file_params
params.require(:file).permit(:name, :content)
end
end
In the above code, we have a FileController that handles the creation of new files. The create method is responsible for this action. The file_params method is used to whitelist the parameters that can be used when creating a new file.
The vulnerability here lies in the fact that there is no server-side check to ensure that the authenticated user has the necessary permissions to create a file. The only protection in place is the before_action :authenticate_user!, which only checks if the user is authenticated, not their level of authorization.
An attacker who has authenticated access but is restricted from file creation can bypass the front-end button disabling by directly sending a POST request to the file creation endpoint. Since there is no server-side check for user permissions, the file will be created. This is a serious security vulnerability as it allows unauthorized file creation.
Steps
- Perform the authorization check in the backend before creating the file.
- Ensure that the authenticated user has the necessary permissions to create a file.
- Implement proper input validation and sanitization to prevent any malicious file creation.
- Use a secure file storage mechanism to store the created files.
- Implement proper error handling and logging to detect and respond to any unauthorized file creation attempts.
Compliant code
class FileController < ApplicationController
before_action :authenticate_user!
before_action :authorize_user!
def create
@file = File.new(file_params)
if @file.save
render json: @file, status: :created, location: @file
else
render json: @file.errors, status: :unprocessable_entity
end
end
private
def file_params
params.require(:file).permit(:name, :content)
end
def authorize_user!
unless current_user.can_create_file?
render json: { error: 'You are not authorized to create files' }, status: :forbidden
end
end
end
The updated code includes a new before_action filter, authorize_user!, which checks if the currently authenticated user has the necessary permissions to create a file. This is done by calling a hypothetical can_create_file? method on the current_user object. If the user does not have the necessary permissions, a JSON response with an error message is rendered and the request is halted with a 403 Forbidden status.
This ensures that the authorization check is performed on the server-side, which is more secure than client-side checks as they can be easily bypassed.
In addition, the file_params method is used to perform input validation and sanitization, ensuring that only the :name and :content parameters are permitted for the file creation. This helps to prevent any malicious file creation attempts.
The create method uses a secure file storage mechanism (in this case, the File.new method) to store the created files. If the file creation is successful, a JSON response with the file details is rendered with a 201 Created status. If the file creation fails, a JSON response with the file errors is rendered with a 422 Unprocessable Entity status.
Finally, proper error handling and logging is implemented to detect and respond to any unauthorized file creation attempts. This is done by rendering a JSON response with an error message and a 403 Forbidden status if the user does not have the necessary permissions to create a file.